High gain space antennas have a number of military and civilian uses, including (secure or unsecure) point-to-point communications, satellite imaging, and synthetic aperture radar (SAR), as well as for planetary and astrophysics research. In point-to-point communications applications, increasing antenna gain increases the data rates at frequencies of interest, allowing ground users to receive more data (e.g., higher resolution images) using devices with smaller antennas (e.g., handheld devices).
In satellite imaging applications, increasing antenna gain allows higher resolution images to be transmitted to the ground in real time. With conventional satellite antennas, satellite images must be transmitted at lower resolutions because of limited available bandwidth.
Synthetic aperture radar uses the motion of the radar antenna to create images of objects on the ground with a finer spatial resolution than is possible with conventional beam-scanning radars. In SAR applications, increasing antenna gain enables the SAR to capture images with higher resolution and better contrast (i.e., greater sensitivity).
Antenna gain may be increased by increasing the diameter of the antenna. Conventional large diameter antennas, however, often have complex deployment mechanisms and, due to their mass and volume, are expensive to transport into space and place in orbit. Some high gain antennas may even require a dedicated launch vehicle.
FIGS. 1A and 1B are diagrams that illustrate conventional spacecrafts 100 and 101, including conventional parabolic antennas 120 and 121.
FIG. 1A illustrates a conventional spacecraft 100 with a conventional ribbed (i.e., umbrella) antenna structure 120. The parabolic antenna structure 120 includes ribs 122 to maintain the parabolic shape. In the past the complexity of the rib structure has led to notable deployment failures (e.g., the Galileo Jupiter probe shown in FIG. 1A). Because the parabola does not collapse in three dimensions, the launch volume of the conventional antenna structure 120 is proportional to the cube of the linear dimension.
FIG. 1B illustrates a conventional spacecraft 101 with a solid parabolic dish 121 stowed for transport in a rocket fairing 180. Because the parabola does not collapse in three dimensions, the launch volume of the parabolic dish 121 is proportional to the cube of the linear dimension.
Because of their size and weight, conventional satellites are expensive to deploy. A satellite with a conventional 5 m antenna, for example, may have a mass of approximately 50 to 80 kilograms and a stowed volume of approximately 1×106 cubic centimeters. Conventional satellites 100 and 101 also require significant power and include large, heavy components such as a transmitter, power management, and thermal control.
Additionally, in order to reposition a conventional satellite antenna and direct the beam to a new location, the entire satellite must be rotated. The components necessary to rotate a satellite add to the cost to manufacture the satellite and, because they add additional size and weight, further increase the cost to deploy the satellite.
Because of the expense to deploy conventional high gain spacecraft antennas, there is a need for a high gain antenna with a reduced stowed volume and the weight. Additionally, there is a need for a high gain spacecraft antenna that can be repositioned without repositioning the entire spacecraft.